U.S. patent number 7,774,931 [Application Number 11/414,139] was granted by the patent office on 2010-08-17 for method of fabricating an integrated intraocular retinal prosthesis device.
This patent grant is currently assigned to California Institute of Technology, University of Southern California. Invention is credited to Hossein Ameri, Mark Humayun, Wen Li, Damien C. Rodger, Yu-Chong Tai, Armand R. Tanguay, Jr., James D. Weiland.
United States Patent |
7,774,931 |
Tai , et al. |
August 17, 2010 |
Method of fabricating an integrated intraocular retinal prosthesis
device
Abstract
Intraocular retinal prosthesis devices and methods for
fabricating the same. A prosthesis device includes a cable region
that connects an electrode array region with a power and data
management region. The electrode array region includes one or more
arrays of exposed electrodes, and the power and data management
region includes various power and control elements. The power and
data management elements, in one aspect, include an RF coil or
coils and circuit arrangements and/or chips configured to provide
drive signals to the electrodes via a cable and receive power and
signals from the RF coil or coils. Each region includes elements
fabricated on or in a single polymer layer during the same
fabrication process.
Inventors: |
Tai; Yu-Chong (Pasadena,
CA), Rodger; Damien C. (South Pasadena, CA), Li; Wen
(East Lansing, CA), Humayun; Mark (Glendale, CA),
Weiland; James D. (Valencia, CA), Ameri; Hossein
(Galveston, TX), Tanguay, Jr.; Armand R. (Yorba Linda,
CA) |
Assignee: |
California Institute of
Technology (Pasadena, CA)
University of Southern California (Los Angeles, CA)
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Family
ID: |
37215522 |
Appl.
No.: |
11/414,139 |
Filed: |
April 28, 2006 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20060282128 A1 |
Dec 14, 2006 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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60675645 |
Apr 28, 2005 |
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60790666 |
Apr 10, 2006 |
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Current U.S.
Class: |
29/832; 607/116;
29/831; 29/847; 607/141; 29/592.1; 607/53; 29/885 |
Current CPC
Class: |
A61N
1/0543 (20130101); A61F 9/08 (20130101); A61N
1/36046 (20130101); Y10T 29/49156 (20150115); Y10T
29/49224 (20150115); Y10T 29/49002 (20150115); Y10T
29/49128 (20150115); Y10T 29/4913 (20150115) |
Current International
Class: |
H05K
3/30 (20060101) |
Field of
Search: |
;29/592.1,831,832,847,885 ;607/53,116,141 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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WO 2004/014479 |
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Feb 2004 |
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WO |
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WO 2004/014479 |
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Feb 2004 |
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WO |
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WO 2006/116625 |
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Nov 2006 |
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WO |
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Other References
Banks, R.H. "Laser Generated Conductive Lines," IBM Technical
Disclosure Bulletin, Aug. 1976, vol. 19, No. 3, p. 1014. cited by
other .
Curcio, C.A. et al., "Topography of Ganglion-Cells in Human
Retina," The Journal of Comparative Neurology, 1990, vol. 300, pp.
5-25. cited by other .
International Search Report mailed on Jul. 7, 2008, for PCT
Application No. PCT/US06/16070 filed on Apr. 28, 2006, 4 pages.
cited by other.
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Primary Examiner: Kim; Paul D
Attorney, Agent or Firm: Townsend and Townsend and Crew LLP
Gray; Gerald T.
Government Interests
STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSORED
RESEARCH OR DEVELOPMENT
The government may have certain rights to the invention based on
National Science Foundation Grant EEC-0310723.
Parent Case Text
CROSS-REFERENCES TO RELATED APPLICATIONS
This application claims the benefit of U.S. Provisional Application
No. 60/675,645, filed Apr. 28, 2005, and 60/790,666, titled
"Retinotopic Layout for Retinal Prosthesis" filed Apr. 10, 2006,
the disclosures of which are each incorporated herein by reference
in its entirety.
Claims
What is claimed is:
1. A method of fabricating an integrated intraocular retinal
prosthesis device having an electrode array region, a power and
data management region and a cable region connecting the electrode
region with the power and data management region, the method
comprising: forming a patterned layer of conductive material on a
first layer of polymer material, said patterned conductive layer
defining circuit elements of the power and data management region,
the electrode region and the cable region wherein the circuit
elements of the power and data management region include one or
more RF coil elements formed of the conductive material; covering
the patterned conductive layer with a second polymer layer; and
removing a portion of the second polymer layer in the electrode
array region so as to expose at least a portion of the patterned
conductive layer to form an exposed electrode array.
2. The method of claim 1, wherein the conductive material comprises
carbonized parylene.
3. The method of claim 1, wherein the conductive material comprises
a conductive metal selected from the group consisting of gold,
platinum, chromium, titanium, platinum and iridium oxide.
4. The method of claim 1, wherein the first polymer layer and the
second polymer layer each comprise one or more of parylene A,
parylene C, parylene AM, parylene F, parylene N, parylene HT or
parylene D.
5. The method of claim 1, wherein the device includes one or more
retention elements configured to retain the RF coil elements in an
implant region of an eye.
6. The method of claim 1, wherein forming the patterned conductive
layer comprises: depositing a layer of photoresist on the polymer
layer; patterning the photoresist with a mask; removing the
patterned photoresist to expose the polymer layer; depositing the
conductive material on the exposed polymer layer; and removing the
remaining photoresist.
7. The method of claim 6, wherein depositing the conductive
material includes one of an e-beam evaporation process, a
sputtering process or an electroplating process.
8. The method of claim 1, further comprising: depositing a layer of
photoresist on a substrate; and forming the first layer of polymer
material on the photoresist.
9. The method of claim 8, wherein the substrate comprises a
material selected from the group consisting of silicon, glass, and
quartz.
10. The method of claim 9, further comprising removing the
photoresist layer so as to separate the device from the
substrate.
11. The method of claim 1, wherein the cable region includes one or
more conductive lines formed of the conductive material, said lines
coupling the electrode array with one or more circuit elements in
the power and data management region.
12. The method of claim 1, wherein the circuit elements of the
power and data management region include one of a chip or a circuit
arrangement configured to provide control signals to the electrode
array.
13. The method of claim 1, wherein the exposed electrode array
includes electrodes arranged in a pattern that mimics the density
pattern of ganglion cells in a retina.
14. The method of claim 1, wherein the exposed electrode array
includes electrodes arranged in a pattern having an irregular
density.
15. The method of claim 1, wherein removing a portion of the second
polymer layer comprises: depositing a layer of photoresist on the
second polymer layer; patterning the photoresist with a mask;
removing the patterned photoresist to expose portions of the second
polymer layer; and etching the exposed portions of the second
polymer layer.
16. A method of fabricating an integrated intraocular retinal
prosthesis device having an electrode array region, a power and
data management region and a cable region connecting the electrode
region with the power and data management region, the method
comprising: forming a patterned layer of conductive material on a
first layer of polymer material, said patterned conductive layer
defining circuit elements of the power and data management region,
the electrode region and the cable region, wherein the cable region
includes one or more conductive lines formed of the conductive
material, said lines coupling the electrode array with one or more
circuit elements in the power and data management region; covering
the patterned conductive layer with a second polymer layer; and
removing a portion of the second polymer layer in the electrode
array region so as to expose at least a portion of the patterned
conductive layer to form an exposed electrode array.
Description
BACKGROUND OF THE INVENTION
The present invention relates generally to retinal prosthesis
devices, and more particularly to integrated retinal prosthesis
devices and methods of manufacturing one or multiple such devices
in monolithic processes.
Intraocular retinal prostheses typically can be considered to
comprise three separate subsystems. One subsystem typically
includes a radiofrequency coil for power and data transmission and
recovery to an externally placed coil. A second subsystem typically
includes a multielectrode array for retinal stimulation. The third
subsystem typically includes an integrated circuit or discrete
components for power recovery and data decoding with analog and/or
digital circuitry for driving the electrode array. FIG. 1 shows and
example of such a prosthesis and its component subsystems.
However, these three components are fabricated as separate
components and combined to form the prosthesis system. This
typically requires multiple fabrication processes, e.g., one for
each device component, in addition to a process for interconnecting
and coupling the various components together to form the prosthesis
system. Such an overall system fabrication process can be overly
complex and time consuming and inefficient. Additionally, the
electrode arrays do not take into consideration the topology of the
target retinal cells to be stimulated.
Therefore it is desirable to provide systems and methods that
overcome the above and other problems. In particular, it is
desirable to provide systems and methods that are fast and reliable
and which allow for multiple system components to be fabricated in
a monolithic fabrication process. It is further desirable that such
systems include electrode arrays that are optimized for enhanced
retinal stimulation.
BRIEF SUMMARY OF THE INVENTION
The present invention provides intraocular retinal prosthesis
systems and methods for fabricating the same. In one aspect,
fabrication of all or multiple components of a prosthesis device or
system are combined into a single monolithic fabrication process.
Also, many such entire systems can be fabricated simultaneously in
a single microfabrication processing run. Additionally, the
geometries of a batch-fabricated device are considered in order for
the system to be implantable and functional within the intraocular
space.
A device according to the present invention includes a cable region
that connects an electrode array region with a power and data
management region. The electrode array region includes one or more
arrays of exposed electrodes, and the power and data management
region includes various power and control elements. For example,
the power and data management elements, in one aspect, include an
RF coil or coils and circuit arrangements and/or chips configured
to provide drive signals to the electrodes via a cable and receive
power and signals from the RF coil or coils. Each region includes
elements fabricated on a polymer layer during the same fabrication
process.
Advantageously, the present invention provides a system that
combines all components in a single, integrated
intraocularly-implantable device. In certain aspects, the
components of the device structure have optimized geometries that
enable implantation and enhanced functionality of the complete
system, and have determined optimal subsystem locations within the
eye. This mechanical design has been demonstrated using parylene as
the bulk substrate, but can be fabricated using different materials
and in many alternative geometries. In one aspect, the portion of
the device to be implanted in the lens capsular bag is configured
with retention elements that anchor that portion in the lens
capsular bag and decreases traction or pulling of the device in
this region into the vitreous cavity, e.g., due to the cable
(cabling effect).
In one aspect, an electrode array is provided that has an exposed
electrode pattern density configured to match the topology of the
target cells to be stimulated, e.g., ganglion cells of the
retina.
According to one aspect of the present invention, a method is
provided for fabricating an integrated intraocular retinal
prosthesis device having an electrode array region, a power and
data management region and a cable region connecting the electrode
region with the power and data management region. The method
typically includes forming a patterned layer of conductive material
on a first layer of polymer material, the patterned conductive
layer defining circuit elements of the power and data management
region, the electrode region and the cable region, and covering the
patterned conductive layer with a second polymer layer. The method
also typically includes removing a portion of the second polymer
layer in the electrode array region so as to expose at least a
portion of the patterned conductive layer to form an exposed
electrode array. In certain aspects, the first polymer layer and
the second polymer layer each include one or more of parylene A,
parylene C, parylene AM, parylene F, parylene N, parylene HT or
parylene D. In certain aspects, the conductive material includes
one or more of carbonized parylene, gold, platinum, chromium,
titanium, platinum and iridium oxide. In certain aspects, the
circuit elements include one or more RF coils. In certain aspects,
the device includes one or more retention elements configured to
retain at least a portion of the circuit elements in an implant
region of an eye. In certain aspects, the exposed electrode array
includes electrodes arranged in a pattern having an irregular
density and/or a density pattern that mimics the pattern of
ganglion cells in a retina.
According to another aspect of the present invention, an integrated
intraocular retinal prosthesis device formed on a layer of polymer
material is provided. The device typically includes a first region
including a plurality of electrodes, a second region including one
or more RF coils and a plurality of control circuit elements
coupled with the one or more RF coils. The device also typically
includes a third region including an interconnect medium having one
or more conductive lines that couple the electrodes with the
plurality of control circuit elements, wherein the control circuit
elements and each of the three regions are fabricated on or in the
same polymer layer. In certain aspects, the polymer layer includes
one or more of parylene A, parylene C, parylene AM, parylene F,
parylene N, parylene HT or parylene D. In certain aspects, the
conductive lines includes one or more of carbonized parylene, gold,
platinum, chromium, titanium, platinum and iridium oxide. In
certain aspects, the exposed portions of the electrodes are
arranged in a pattern having an irregular density and/or a density
pattern that mimics the pattern of ganglion cells in a retina.
According to yet another aspect, the present invention provides an
integrated prosthesis device implanted in an eye wherein the first
region is located proximal to the retina, and wherein the second
region is located within or proximal to a capsular bag region of
the eye. In certain aspects, the device includes one or more
retention elements configured to retain the RF coils in an implant
region of an eye. In certain aspects, control circuit elements are
included in the second region.
Reference to the remaining portions of the specification, including
the drawings and claims, will realize other features and advantages
of the present invention. Further features and advantages of the
present invention, as well as the structure and operation of
various embodiments of the present invention, are described in
detail below with respect to the accompanying drawings. In the
drawings, like reference numbers indicate identical or functionally
similar elements.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 illustrates a typical intraocular retinal prosthesis system
and the approximate locations of the system components when
implanted in an eye.
FIG. 2 illustrates the chemical structures of the three most common
parylenes.
FIG. 3 illustrates an example of a prosthesis device according to
one embodiment of the present invention.
FIG. 4 illustrates examples of fabricated or partially fabricated
prosthesis devices in comparison with a penny.
FIG. 5 illustrates an example of a prosthesis device implanted in
an enucleated pig's eye.
FIG. 6 illustrates an overhead depiction and approximate geometry
and sizes of a prosthesis device including an RF coil with "ear"
shaped retention elements.
FIG. 7 illustrates an angled view of a prosthesis device including
an RF coil with leaves/rabbit ears.
FIG. 8 illustrates an underside view of a prosthesis device
including an RF coil with leaves/rabbit ears.
FIG. 9 illustrates a prosthesis device including an RF coil region
with "anchor" shaped retention elements.
FIG. 10 is a graph showing ganglion cell densities in the retina as
a function of radial position.
FIG. 11 shows an example of a "retinotopic" electrode array layout
according to one embodiment.
FIG. 12 is a graph showing approximate radial densities of
electrodes in a pattern that more closely matches the density
pattern of ganglion cells as shown in FIG. 10.
FIG. 13 illustrates an example of a fabricated device with a
retinotopic array layout according to one embodiment.
FIG. 14 is an SEM image of a fabricated electrode array according
to one embodiment.
FIG. 15 illustrates an RF coil arrangement according to one
embodiment. As shown, a chip, or circuit arrangement is located
within the RF coil region.
FIG. 16 illustrates a prosthesis device including the arrangement
of FIG. 15 according to one embodiment.
FIG. 17 illustrates the prosthesis device of FIG. 16 rolled up to
match the topology of the eye.
FIGS. 18-20 illustrate different views of the positioning and
layout of the device of FIG. 16 when implanted in an eye.
FIG. 21 illustrates the anatomy of an eye as a reference.
DETAILED DESCRIPTION OF THE INVENTION
The present invention provides intraocular prosthesis systems and
devices and methods of manufacturing the same. In one embodiment,
all or a portion of the components of an intraocular prosthesis
system or device are fabricated in a monolithic fabrication
process. Additionally, multiple systems can be fabricated in a
single batch fabrication process.
A prosthesis device according to one embodiment of the invention
includes a power and data management subsystem, a retinal
stimulation subsystem and an interconnect medium for providing
signals between the power and data management subsystem and the
retinal stimulation subsystem. In one aspect, the power and data
management subsystem includes one or several radio-frequency (RF)
coils and one or several intelligence modules, e.g., circuit
arrangements or packaged chips. The stimulation subsystem includes
one or several multielectrode array regions. In certain aspects, a
multielectrode array includes electrodes arranged with a density
pattern that is optimized to stimulate the ganglion cells in the
retina. One or several connection cables interconnect the electrode
arrays with the intelligence module(s) to allow for control of an
electrode array by an intelligence module.
A device according to one aspect is fabricated using one or several
polymers as the bulk substrate material, although substrate
materials such as silicon, glass, etc may be used as a platform for
device formation. A metal and/or a conductive polymer and/or other
conductive materials form the connection lines embedded within the
cables and other device regions. The final geometry of the system
is formed in the polymer material, e.g., etched using oxygen plasma
or other techniques (e.g. excimer laser, blade) and where a
substrate/platform is used for fabrication, the device is removed
from the substrate.
In certain aspects, parylene is used as the base material for
device fabrication due, in part, to its proven biocompatibility and
its ease of integration with standard microfabrication processes
and techniques. Parylene is a USP Class VI biocompatible polymer
that can be deposited through a highly-conformal vapor deposition
process. Types of parylene include parylene C, F, A, AM, N, D and
HT. Of the three most common types of parylene, shown in FIG. 2,
parylene C is perhaps the most widely used in industry. The
advantages of the use of parylene include its proven
biocompatibility, its strength and flexibility (e.g., Young's
modulus .apprxeq.4 GPa), its conformal pinhole-free
room-temperature deposition, its low dielectric constant
(.apprxeq.3) and high volume resistivity (>10.sup.16
.OMEGA.-cm), its transparency, and its ease of manipulation using
standard microfabrication techniques such as reactive ion etching
(RIE). Several research groups have used parylene C deposition as a
method of creating a biocompatible, water-blocking seal around
electrode arrays typically fabricated using a polyimide substrate.
This is necessary because most polyimides have a moisture
absorption that is more than an order of magnitude higher than that
of parylene C. Some specialized polyimide films have lower moisture
absorption, but they require high-temperature curing steps that are
generally not post-IC compatible, and their use in permanent
medical implants is not permitted.
FIG. 3 illustrates a prosthesis device 10 according to one
embodiment. As shown, device 10 includes a retinal stimulation
subsystem 20 including one or more electrode arrays and a power and
data management subsystem 30, including one or several RF coils 32
and one or several intelligence modules 34. An interconnect medium
40 couples the retinal stimulation subsystem 20 with the
intelligence modules 34. As shown in FIG. 3, the various subsystems
and components of device 10 are marked, and may be referred to
hereafter, as "RF Coil", "chip", "cable" and "electrode array".
In one aspect, subsystem 30 includes a polymer-based RF coil having
one or several layers of conducting lines embedded therein. The
coil is designed, in one aspect, to be placed in the capsular bag
(region of crystalline lens with lens removed) or in the sulcus
just anterior to this region. In one aspect, optional suture loops
or holes are provided so that the device can be sutured or fastened
to the capsule, ciliary body, or sclera. See, e.g., FIG. 21 for a
view of the anatomy of an eye. In one aspect, the approximate
diameter of the RF coil outline is between about 9 mm and about 13
mm. However, the diameter can be smaller or larger and the precise
topology and morphology of the RF coil region (and the optional
suture holes or loops) can be varied according to the specific
implementation. According to one aspect, the regions to the right
of the RF coil region in FIG. 3 are designed to be threaded through
a surgically-defined incision in the posterior capsule into the
vitreous cavity (see FIG. 21 for eye anatomy; the region posterior
to the lens in the posterior segment is the vitreous cavity).
Subsystem 30 also includes one or more circuit arrangements or
chips 34. The chip(s) is/are responsible for power and data
recovery from the RF coil, and driving of the individual electrodes
on the electrode array. In certain aspects, for example, a circuit
arrangement or chip includes elements for receiving and storing
electrical energy and delivering the electrical energy to various
system components, elements for storing data and providing control
signals to an electrode array and elements for receiving signals
and/or energy from an RF coil. In certain aspects, as shown in FIG.
3, a chip 34 is located on cable 40 proximal the RF coil region.
However, a chip may be located elsewhere in the device. For
example, a chip may be located within the RF coil region and
contained within the capsular bag when implanted (see, e.g., FIG.
15), or a chip can be located closer to the electrode array region.
In one aspect, one or more chips are electrically connected to both
the RF coil and electrode array region using one or a plurality of
conductive lines fabricated of metal, conductive polymer or other
conductive materials. In certain aspects, defined regions, e.g.,
interconnect holes, in the polymer are provided to expose portions
of the conductive materials. The interconnect holes can be defined
during device fabrication using oxygen plasma etching (masked by
photoresist) or excimer laser ablation, or other techniques. The
chip region(s) are ideally encased and/or embedded within polymers
or a metallic package, but other packaging materials and
technologies can be used. The precise geometry/geometries of the
chip region(s) can be varied, however, in certain aspects it is
desirable that each chip does not exceed approximately 10
mm.times.10 mm to facilitate implantation.
In certain aspects, the cable 40 includes one or more conductive
lines embedded within one or several layers of the cable polymer.
The cable connects the chip(s) to the electrode array region. In
one aspect, to facilitate implantation in an eye, the total length
of the cable region is about 10 mm to about 20 mm, and the width is
about 1.0 mm to about 10 mm. The width can be varied because the
cable is foldable or rollable so as to fit through the posterior
capsule incision upon implantation.
Stimulation subsystem 20, in certain aspects, includes one or more
electrode arrays. In one aspect, the electrode array is circular as
shown, having a diameter of between about 1 mm and about 10 mm (1
cm) in diameter. However, the array does not have to be circular in
nature as shown in FIG. 3, but can be of any reasonable shape such
as square or rectangular (see, e.g., FIG. 11), and of any
reasonable size depending upon the desired application. To
facilitate implantation in an eye, for example, the electrode array
should be approximately 5 mm in diameter, but can be smaller or
larger depending on the specific implementation (because this
region is foldable/rollable, it can fit through small incisions).
The electrodes within the array are exposed by oxygen plasma
etching or excimer laser ablation, or some other method during
device fabrication. As shown, an optional retinal tack region is
provided for insertion of a retinal tack for connection of the
array to the retina. The location and geometry of the tack region
can be varied. Also as shown, an optional loop is provided for
facilitating surgical manipulation, however other techniques can be
used to facilitate surgical implantation (e.g. post, hole for
forceps, etc.). In certain aspects, an electrode array (and other
polymer fabricated elements) can be heat formed to match curvatures
of the eye to facilitate implantation.
In certain aspects, when parylene (e.g., parylene C) is used as the
base device material, it is desired that each region or subsystem
of the device have a thickness of between about 5 .mu.m and about
30 .mu.m (the thicknesses from region to region do not have to be
the same), although thicker layers may be used. Regions of the
device can be heat-formed or molded to specifically match the
curvature of various aspects of the eye. Examples of devices
fabricated according to one embodiment (but without conductive
lines) are shown in FIG. 4. As shown in FIG. 5, these devices have
since been implanted in enucleated pig eyes as a surgical
demonstration.
According to one embodiment, the RF coil region includes a one or
more retention elements to facilitate mechanical retention of the
RF coil region within the capsular bag or anterior to it as shown
in FIGS. 6-9. Examples of retention elements are the "rabbit ear"
shaped elements as depicted in FIG. 6, and the "anchor" shaped
elements of FIG. 9, in which the RF coil is situated in the
continuous polymer region to the left of the dotted line. This
morphology includes regions ("ears") protruding beyond the location
at which the cable attaches to the RF coil region (and not directly
attached to the cable). The retention elements are able to maintain
the integrity of the capsule and retain the RF coil and capsular
regions within the capsule even though the cable may bend (and thus
exert a pulling force) when exiting this region. Thus, the
advantage of the retention elements is the resistance force they
provide when the device is implanted; the bending and threading of
the electrode array and cable regions through the posterior capsule
would not, by traction and the connection of the cable with the RF
coil region, pull the coil into the vitreous cavity as well because
they are not directly connected to this cable but are instead
connected through the bulk of this region depicted on the left. As
shown in FIG. 15, for example, a chip could reside within the RF
coil region (thus within the capsule or anterior to it), at the
point of attachment of the cable, or could, as depicted in FIG. 6,
be situated along the cable region within the vitreous cavity. The
precise geometry and morphology of the RF coil with retention
elements can be varied, and the suture holes depicted are
optionally provided to facilitate securing the device during
implantation. Additionally, other mechanisms of attachment or
further fastening of the device within the capsule can be
employed.
In one embodiment, the subsystems and components of a prosthesis
device 10 are all fabricated together during the same monolithic
production process or run. An example of a process for fabricating
an integrated device 10 according to one embodiment follows. In one
aspect, a sacrificial layer of photoresist is first formed on a
substrate as a release layer. The substrate can include any of a
variety of materials such as silicon, glass, quartz, etc. A polymer
such as parylene is then deposited, and conductive lines are then
patterned on the polymer, e.g., using conventional masking
techniques. In one aspect, a patterned layer of conductive material
is formed to define one or more of the various subsystem components
such as the RF coils, the chip elements, the interconnection cable
lines and/or the electrodes. Conductive lines are formed by
depositing a metal, a conductive polymer or other conductive
material. The conductive material can be deposited by evaporation,
sputtering, or electroplating, for example. In preferred aspects,
the conductive material includes a metal material. Useful metals
include titanium, platinum, platinum grey, platinum black,
chromium, gold, iridium oxide, and others. In other aspects, the
conductive material includes any electrically conducting medium
such as a conducting polymer, a doped semiconductor material,
graphite, or a combination of these conductive materials. One
useful conductive polymer is carbonized parylene. Parylene can be
carbonized either by exposing it in a hot furnace (preferably
unoxygenated gas like nitrogenous gas) or by ion
bombardment/implantation of parylene with carbon atoms. In the
latter case, a mask can be used to mask off those areas that should
not be carbonized (e.g., using a stencil, photoresist, metal, or
other masking means). It should be appreciated that one or more
different conductive materials can be used for different circuit
elements, and that the various circuit elements can be formed of
different materials. For example, the conductive lines in the cable
region can be formed of carbonized parylene, the electrodes formed
of a second material and the RF coil and chip elements formed of
the same or different conductive material(s).
Another layer of polymer material (e.g. parylene) is then deposited
to seal the conductive material. Any regions requiring exposure for
electrical contact to the retina (e.g., electrodes in the retinal
stimulation subsystem) or elements in other region are then opened
(e.g., by oxygen plasma etching, excimer laser ablation, etc.). It
should be appreciated that multiple conductive line patterning and
polymer deposition steps may occur as needed, e.g., to define
components and circuits for the power and data management subsystem
30. For example, U.S. patent application Ser. No. 11/130,814,
titled "PARYLENE-BASED FLEXIBLE MULTI-ELECTRODE ARRAYS FOR NEURONAL
STIMULATION AND RECORDING AND METHODS FOR MANUFACTURING THE SAME,"
filed May 16, 2005, and which is hereby incorporated by reference
in its entirety, discloses examples of devices including multiple
conductive layers and multiple parylene layers and methods for
fabricating such devices.
The precise geometry of the device 10 can then be defined by
masking off the device region by photoresist or some other method
and etching the polymer surrounding the device away (or using other
methods to cut or etch). The photoresist release layer can then be
removed, separating the device from the substrate. In this manner,
a single prosthesis device, including all of the components or
subsystems, can be fabricated simultaneously in the same run, for
instance, using standard microfabrication techniques. Additionally,
multiple devices can be fabricated simultaneously in a batch
fabrication process. For example, multiple devices can be formed
simultaneously on a wafer. It should be appreciated that the
precise geometries/morphologies of the device can be varied to
accommodate different eyes, shapes, and surgical
procedures/considerations.
It should be appreciated that devices according to the present
invention are not restricted to one layer of conductive material.
For example, it may be advantageous to provide a device with
several alternative levels of conductors or electrodes. If, for
instance, it is desirable to restrict a cable to a certain
dimension (e.g., width) but keep the lines relatively large, one
line can be run out to an electrode, covered entirely, then the
next line and electrode layed down, the whole structure covered in
polymer, and then all the electrodes opened up. One of the
electrodes would be recessed by the thickness of the polymer
covering the first line and electrode. Alternately, the electrode
on the first layer can be formed at the same time as the overlying
line and electrode, provided the underlying trace is first opened
up, e.g., using RIE or laser ablation of the polymer layer.
Electrode Array
As discussed above, an electrode pattern can be formed on a polymer
layer such as parylene, e.g., by masking, exposing and developing a
photoresist layer as is well know. The electrode pattern is
transferred to the parylene layer overlaying the conducting
material to expose the underlying conductive material according to
the desired electrode pattern. In certain aspects, the electrode
pattern is transferred by a plasma etch such as a reactive ion etch
(RIE). In general useful methods for transferring the pattern to
the parylene (e.g., removing parylene) include plasma etching,
laser ablation, blade cutting, melting, or any combination of these
processes. The preferred masking material is photoresist, however
other useful materials include polymers, metals, or a shadow mask
(e.g., a stencil).
According to one embodiment, an electrode pattern includes an
electrode spacing arranged to more closely match the receptors of
target cells. Target cells matched may include photoreceptors,
amacrine, horizontal, bipolar, or ganglion cells, for example. For
example, in one embodiment, the electrode spacing is varied so as
to more closely match the ganglion cell density in the retina. In
certain aspects, the exposed electrodes are arranged in a pattern
that is irregular or variable and not in a grid-like arrangement so
as to better match the target. Because it is thought that
electrical stimulation actually stimulates the ganglion cells, it
is advantageous for the electrode layout to match that of the
ganglion cells. Such a biomimetic electrode layout may lead to
better function for patients by matching the natural visual density
of the ganglion cells. If the target cells were the amacrine or
bipolar cells, then, the electrode array layout could match those
target cell densities instead. Here, such cell density matching is
defined as "retinotopic" matching.
The ganglion cell density measured in human retinas is shown in
FIG. 10. See, C. A. Curcio and K. A. Allen, "Topography of
Ganglion-Cells in Human Retina," Journal of Comparative Neurology,
vol. 300, pp. 5-25, 1990. An electrode array designed so that the
electrode densities more closely match these ganglion cell
densities is shown in FIG. 11. FIG. 12 shows the approximate radial
densities of the electrode designed to match those in FIG. 10.
However, it is important to note that these are not the exact
dimensions and spacings required to match these target cell
densities. In fact, based on the number of electrodes in the array
as well as other considerations, these dimensions and spacings can
be changed. It should be appreciated that the electrode pattern
dimensions and distances may be varied based on electrode size,
number, overall array geometry, target cells matched, or other
considerations.
A fabricated retinotopic electrode array is shown in FIG. 13. FIG.
14 shows a scanning electron micrograph of the electrode array
region of one of these fabricated electrode arrays.
Implantation Example
FIG. 16 shows an example of an integrated prosthesis device
according to one embodiment. FIGS. 17-20 illustrate examples of use
of the prosthesis device according to one embodiment. A shown in
FIG. 17, the prosthesis device of FIG. 16 can be rolled up to match
the topology of the eye. FIGS. 18-20 illustrate the positioning and
layout of the device when implanted in an eye.
While the invention has been described by way of example and in
terms of the specific embodiments, it is to be understood that the
invention is not limited to the disclosed embodiments. To the
contrary, it is intended to cover various modifications and similar
arrangements as would be apparent to those skilled in the art.
Therefore, the scope of the appended claims should be accorded the
broadest interpretation so as to encompass all such modifications
and similar arrangements.
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